For instance, in a solid-state imaging device, a color filter in which colored pixels of plural colors, for example, a red color pixel, a green color pixel or a blue color pixel are two-dimensionally arrayed on a support, for example, a semiconductor substrate is provided. As to the solid-state imaging device, in recent years, increase in the number of pixels is remarkable and when it is compared with a traditional solid-state imaging device having the same inch size, reduction of pixel size is noticeable. Further, along with the reduction of pixel size, performance demand on color separation becomes strict and in order to maintain device performances, for example, color shading performance or color mixing prevention, performances, for example, reduction in thickness, rectangularization or elimination of overlap area in which colors are overlapped between respective colored pixels are required for the color filter.
As a method of producing such a color filter, a photolitho method has been often employed. The photolitho method is a method in which a colored photosensitive composition is coated on a support and dried to form a colored layer and the colored layer is subjected to pattern exposure, development and the like to form a colored pixel of a first color (for example, green color), and then colored pixels of remaining colors are formed in the same manner as above.
However, along with the miniaturization of pixel in the solid-state imaging device, it becomes difficult for pattern formation by a so-called photolitho method to balance a spectral property with a pattern-forming property of color filter toward a request for miniaturization and reduction in thickness of color filter. Specifically, in a color filter for solid-state imaging device, there is a tendency to seek the miniaturization so as that as to the reduction in thickness of colored pattern, the thickness is, for example, 1 μm or less and the pixel pattern size is 2 μm or less (for example, from 0.5 to 2.0 μm).
In particular, together with the progress of reduction in thickness, a relative amount of a coloring agent, for example, pigment in a layer increases, on the other hand an amount of a component contributing a photolitho property other than the coloring agent in the layer relatively decreases. With respect to the pattern-forming property due to the decrease of amount of a component contributing a photolitho property, in case of the demand on pattern formation less than 2.0 μm there is a problem, for example, in that the pattern profile by cross-sectional observation has a round pattern edge and is lack of rectangularity even when correction, for example, OPC has been conducted, although the effect of improving the pattern profile is recognized when observed from above. It has been known that in a color filter using a pigment dispersion liquid (a color filter produced by a photolitho method using colored radiation-sensitive compositions in which a pigment is dispersed in various compositions) the round pattern edge becomes prominent owing to light scattering by the pigment at the time of exposure.
In particular, recently, based on the further demand on high-definition in a color filter for solid-state imaging device, for example, a forming property of 1.4 μm pattern has been requested, which is close to the limit of resolution in a hitherto known photolitho method.
Against the method of producing a color filter utilizing the photolitho method, a processing method using a dry etching method has been proposed as a method effective for realizing the miniaturization and reduction in thickness of pattern. The dry etching method has been adopted as a method of forming a pattern (each colored pixel) in a rectangular form, and a pattern-forming method with combination of the photolitho method and dry etching method or the like has been proposed (see, for example, JP-A-2006-222290 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”) and JP-A-2007-48774).